JPH11144678A - Flat light source and liquid crystal display apparatus using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat light source in which spattering of a dielectric layer due to electric discharge is restrained, luminance non-uniformity or flickering or the like is not generated over a long time, and ultraviolet light emitting efficiency is enhanced, and luminance is improved. SOLUTION: In an electric discharge apparatus in which a flat sealing container 1 is constituted by combinating a light-transmittable front plate 10 with an insulation substrate 20, a pair of electric discharge electrodes 40 and 41 parallel to each other is provided on an interior face of the front plate 10, the surfaces of the electric discharge electrodes 40 and 41 are covered with the dielectric layer, a phosphor 60 is applied to an interior face of the insulation substrate 20, and discharge gas is sealed inside the sealing container 1, the discharge gas pressure is selected between 7000 Pa and 40000 Pa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination device and a liquid crystal display device using a flat discharge device which emits light in a planar manner.

[0002]

2. Description of the Related Art Liquid crystal panels are widely used as various types of information video displays such as personal computers and televisions because of their thinness, lightness and low power consumption. A backlight that supplies light from the back of the liquid crystal panel is required. The backlight generally used is mainly a combination of a small-diameter fluorescent lamp and an acrylic resin light guide, but a flat discharge lamp is also used.

FIG. 9 is a sectional view of a conventional flat light source described in, for example, Japanese Patent Application Laid-Open No. 9-115483. As shown in the figure, a translucent front plate 10 made of soda glass or the like.
And an insulating substrate 20 made of soda glass, ceramic, or the like.
The side plate 30 and the side plate 30 are integrally hermetically sealed with, for example, low-melting glass (not shown) to form a flat closed container 1. A pair of discharge electrodes 40 and 41 parallel to each other are provided on the inner surface of the front plate 10 serving as a light emitting surface.
The surface of 41 is covered with a dielectric layer 50. A phosphor 60 is applied on the inner surface of the insulating substrate 20, and a discharge space 70 in the closed vessel 1 is a mercury and mixed gas such as argon or neon-argon as a starting gas, or xenon, krypton, or argon. , Helium, neon, or other rare gas is sealed therein, and the pressure of the rare gas is 600 Pa to 7000 Pa.

[0004] The flat light source according to the present configuration has a discharge electrode 4.
By applying a high-frequency voltage between 0 and 41, a discharge is generated in the discharge space 70, the phosphor 60 is excited by the ultraviolet rays generated by the discharge to emit light, and the light is emitted to the outside through the front plate 10.

[0005]

The conventional flat light source is
When the dielectric layer is sputtered by the discharge and is operated for about 5000 hours, the surface state of the dielectric layer changes, causing uneven brightness and flickering, thereby causing a problem that the discharge is not stably performed.

[0006] In addition, there is a problem that the luminance deteriorates drastically due to the attachment of the sputtered substance to the phosphor surface, the ultraviolet light emission efficiency is low, and the luminance is low and the efficiency is low.

An object of the present invention is to solve the above-mentioned problems and to provide a long-life, high-brightness, high-efficiency flat light source and a lighting device such as a liquid crystal backlight using the flat light source.

[0008]

In order to achieve the above object, the present invention provides a flat closed container having at least a pair of discharge electrodes whose surfaces are covered with a dielectric layer. In a flat light source in which mercury and at least one type of rare gas are sealed, the pressure P of the rare gas is selected between 7000 Pa and 40000 Pa.

Alternatively, a flat closed container is formed by combining a light-transmitting front plate, an insulating substrate, and a side plate, and at least a pair of discharge electrodes are provided on the inner surface of the front plate, and the surface of the discharge electrodes is formed. In a flat light source in which a dielectric layer is provided so as to cover the inner surface of the insulating substrate, a phosphor is applied, and mercury and at least one type of rare gas are sealed in the closed container, the pressure P of the rare gas is set to 7000 Pa. From 4000
Choose between 0 Pa.

Alternatively, using a box-shaped container in which the insulating substrate and the side plate are integrally formed, a phosphor is applied to the inner surface of the box-shaped container.

Further, a spacer is provided inside the closed container.

Further, a phosphor is applied to the front plate.

[0013] Further, the lighting device is configured to illuminate using the above-described discharge device.

In the liquid crystal display device, the above-described discharge device is used as a backlight.

[0015]

FIG. 1 is a sectional view showing an embodiment of a flat light source according to the present invention. As shown in the figure, a translucent front plate 10 made of, for example, soda glass, an insulating substrate 20 made of soda glass, ceramic, or the like, and a side plate 30 are integrally hermetically sealed with, for example, low-melting glass (not shown). Thus, a flat closed container 1 is formed. A pair of parallel discharge electrodes 40 and 41 are provided on the inner surface of the front plate 10, and the surfaces of the discharge electrodes 40 and 41 are respectively covered with dielectric layers 51 and 52 provided by a thick film printing method or the like. I have. By printing the dielectric layer only on the discharge electrodes, the transmittance of the front plate 10 increases, and the light extraction efficiency improves.

A phosphor 60 is applied to the inner surface of the insulating substrate 20, and a discharge space 70 in the closed vessel 1 is filled with a mixed gas of mercury and a rare gas such as argon or neon-argon. The rare gas is enclosed alone or as a mixture of two or more. An appropriate pressure may be selected in the range of 7,000 Pa to 40,000 Pa. When two or more rare gases are used as a mixture, the filling pressure is the total pressure.

As shown in FIGS. 2A and 2B, the driving method of the flat discharge device according to the present embodiment is, for example, as shown in FIG.
Has a rectangular wave voltage V1 having a voltage of -Vh indicated by 45.
To the electrode 41, a rectangular wave voltage V2 of 46 is shifted from the 45 by a half cycle. By using such a driving method, a discharge is generated in the discharge space 70, and the phosphor 60 is excited by the ultraviolet rays generated by the discharge to emit light, and the light is emitted to the outside through the front plate 10. Period f of square wave voltage
May be appropriately selected in the range of 2 kHz to 1 MHz. The duty ratio defined by W2 / W1 in FIG. 2A may be appropriately selected from a range of 1% to 50%.

FIG. 3 is a characteristic diagram showing the relationship between the operating time of the flat light source shown in FIG. 1 and the stable operating voltage range.
This figure shows a case where argon is sealed at 2660 Pa. The stable operation voltage region with good luminance uniformity is 200 V from 600 V to 800 V in the initial stage of lighting.
After 0 hour, the voltage drops to 50V. After 5,000 hours, the stable operation voltage region becomes 0 V, and uneven brightness and concentration of discharge occur. Therefore, the uniformity is deteriorated and the device cannot be used for a backlight or the like. This is because the dielectric layer is sputtered by the discharge,
This is because the surface state of the dielectric layer has changed.

When the pressure for filling the rare gas is increased, the dielectric layer is less likely to be sputtered and the surface state is less likely to change. Therefore, when the sealing pressure is increased, the stable operation time becomes longer, and the life is extended. The operation time of the flat light source needs to be about 15,000 hours from the system use time, and from the results of this experiment, it is desirable that the rare gas sealing pressure be 7000 Pa or more to satisfy the life.

FIG. 4 is a characteristic diagram showing the relationship between the argon filling pressure and the luminance of the flat light source shown in FIG. The luminance sharply increases as the sealing pressure increases up to 7000 Pa, and gradually increases even at 7000 Pa or more.
Therefore, in order to increase the luminance, the rare gas sealing pressure is set to 70.
It is necessary that the pressure be at least 00 Pa.

FIG. 5 is a characteristic diagram showing the relationship between the argon filling pressure and the starting voltage of the flat light source shown in FIG.
The starting voltage is 800 V when the sealing pressure is 5000 Pa, but increases to 2000 V at 40000 Pa as the sealing pressure increases. If the starting voltage is 2000 V or higher, the voltage is too high and driving using a transformer becomes impossible. In addition, when driven by a circuit configuration that does not use a transformer, electronic components having a high withstand voltage are required, and the cost is significantly increased. Therefore, it is necessary to set the rare gas charging pressure to 40,000 Pa or less due to the configuration of the drive circuit, restrictions on parts used, and the like.

FIG. 6 is a sectional view showing another flat light source according to the present invention. As shown in the figure, for example, an insulating substrate 21 integrated with a side plate, that is, a box-shaped container made by thermoforming a glass plate, and a front plate 10 are hermetically sealed to form a flat closed container 1. A pair of parallel discharge electrodes 40 and 41 are provided on the inner surface of the front plate 10, and the surfaces of the discharge electrodes 40 and 41 are covered with dielectric layers 51 and 52 provided by a thick film printing method or the like, respectively. , Insulating substrate 2
A phosphor 60 is applied to the inner surface of the closed container 2.
A mixed gas of mercury and a rare gas such as argon or neon-argon is supplied from 7000 Pa to 4000
It is sealed in the range of 0 Pa.

In this flat light source, the closed container 1 is constituted by the insulating substrate 21 and the front plate 10 integrated with the side plates, so that the assembly is simplified and the manufacturing cost is reduced. Also in this flat light source, FIGS.
Since an experiment result similar to the experiment result shown in FIG. 5 is obtained, the rare gas charging pressure is increased from 7000 Pa to 40000 Pa
By doing so, a long-life, high-brightness, high-efficiency flat light source can be obtained.

FIG. 7 is a sectional perspective view showing still another flat light source according to the present invention. In this embodiment, a spacer 80 having a substantially triangular cross section is inserted into the discharge space 70 of the flat light source shown in FIG. 1 and provided in a direction crossing the discharge electrodes 40 and 41 (not shown). The phosphor 60 is formed on the side surface of the spacer 80 facing the front plate 10 or on the insulating substrate 2.
0 is applied to the surface.

The spacer is necessary to increase the light emitting surface of the flat light source or to reduce the weight by reducing the thickness of the front plate or the insulating substrate. The breakage of the face plate and the insulating substrate can be eliminated.

With this flat light source, the same experimental results as those shown in FIGS. 3, 4 and 5 were obtained.
By setting the noble gas sealing pressure from 7000 Pa to 40,000 Pa, a long-life, high-brightness, high-efficiency flat light source can be obtained.

The spacer 80 need not be provided over the entire discharge space, but may be provided only partially. Further, the shape is not limited to the above-described triangle, and may be selected, for example, from a shape that gradually becomes thinner toward the front plate in a stepped shape, or a shape that does not cause luminance unevenness on the light emitting surface, such as a spherical shape or an elliptical shape. Further, the spacer may be integrally formed on the insulating substrate 20 by using a thick film printing method or the like.

FIG. 8 is a sectional view showing still another flat light source according to the present invention. In this embodiment, the phosphor 61 is also applied to the inner surface of the front plate 10 of the flat light source shown in FIG. By applying the phosphor to the front plate, the utilization rate of ultraviolet rays is improved, and the luminance and the luminous efficiency are improved. With this flat light source, the same experimental results as those shown in FIGS. 3, 4, and 5 were obtained. Therefore, by setting the rare gas filling pressure from 7000 Pa to 40,000 Pa, a long-life, high-brightness, high-efficiency flat light source can be obtained.

In the above embodiment, the phosphor 61 is applied to the inner surface of the front plate 10, but may be applied to the upper surfaces of the dielectric layers 51 and 52.

As described in detail above, when the flat light source of the present invention is used in, for example, an illumination device, a long-life, high-efficiency illumination device can be obtained.

When the flat light source of the present invention is used in, for example, a liquid crystal display device, a backlight having a long life and high efficiency can be obtained.

[0032]

In the flat light source according to the present invention, by selecting the pressure P of the rare gas between 7000 Pa and 40000 Pa, a long life, high luminance and high efficiency can be obtained.

Alternatively, a flat closed container is formed by combining a light-transmitting front plate, an insulating substrate, and a side plate, and at least one pair of discharge electrodes is provided on the inner surface of the front plate, and the surface of the discharge electrodes is formed. In a flat light source in which a dielectric layer is provided so as to cover the inner surface of the insulating substrate, a phosphor is applied, and mercury and at least one type of rare gas are sealed in the closed container, the pressure P of the rare gas is set to 7000 Pa. From 4000
By choosing between 0 Pa, long life, high brightness and high efficiency are obtained.

Alternatively, if a box-shaped container in which the insulating substrate and the side plate are integrally formed is used, the assembly is simplified and the manufacturing cost is reduced.

Further, by providing a spacer inside the closed container, damage to the front plate and the insulating substrate can be eliminated.

Further, by applying a phosphor to the front plate, the luminance and efficiency are improved.

In the lighting device and the liquid crystal display device according to the present invention, a device having a long life, high luminance and high efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a flat light source according to an embodiment of the present invention.

FIG. 2 is a drive voltage waveform diagram of a flat light source.

FIG. 3 is a characteristic diagram showing a relationship between an operation time and a stable operation voltage region.

FIG. 4 is a characteristic diagram showing a relationship between a rare gas sealing pressure and luminance.

FIG. 5 is a characteristic diagram showing a relationship between a charged pressure of a rare gas and a starting voltage.

FIG. 6 is a sectional view showing another embodiment of the flat light source according to the present invention.

FIG. 7 is a sectional perspective view showing still another embodiment of the flat light source according to the present invention.

FIG. 8 is a sectional view showing still another embodiment of the flat light source according to the present invention.

FIG. 9 is a sectional view showing a conventional flat light source.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Closed container, 10 ... Front plate, 20, 21 ... Insulating substrate,
Reference numeral 30: side plate, 40, 41: discharge electrode, 45, 46: drive voltage waveform, 50, 51, 52: dielectric, 60, 61: phosphor, 70: discharge space, 80: spacer.

Continuing on the front page (72) Inventor Yasushi Ikuta 888 Fujibashi, Ome-shi, Tokyo Ome Industries Co., Ltd. (72) Inventor Kanji Kiname 888 Fujibashi, Ome-shi, Tokyo Heating Lighting Division, Hitachi, Ltd. (72) Inventor Shigeo Mikoshiba 2-43-17 Izumi, Suginami-ku, Tokyo (72) Inventor Tomokazu Shiga 568, Kitanocho, Hachioji-shi, Tokyo (72) Inventor Keiko Hirayama 4328-7, Oyamacho, Machida-shi, Tokyo

Claims (7)

[Claims] 1. A flat light source comprising a flat closed container having at least a pair of discharge electrodes whose surfaces are covered with a dielectric layer, wherein mercury and at least one rare gas are sealed in the closed container. , The pressure P of the rare gas is set to 700
A flat light source selected from 0 Pa to 40,000 Pa. 2. A flat hermetic container is formed by combining a front plate having translucency, an insulating substrate, and side plates, and at least one pair of discharge electrodes is provided on an inner surface of the front plate, and a surface of the discharge electrodes is formed. In a flat light source in which a dielectric layer is provided so as to cover the inner surface of the insulating substrate, a phosphor is applied, and mercury and at least one type of rare gas are sealed in the closed container, the pressure P of the rare gas is set to 7000 Pa. A flat light source characterized in that the light source is selected from a range between 40 Pa and 40,000 Pa. 3. The flat light source according to claim 2, wherein a box-shaped container in which the insulating substrate and the side plate are integrally formed is used, and a phosphor is applied to an inner surface of the box-shaped container. 4. The flat light source according to claim 2, wherein a spacer is provided inside the closed container. 5. A flat light source according to claim 2, wherein a phosphor is applied to said front plate. 6. An illuminating device configured to illuminate using the flat light source according to any one of claims 1 to 5. 7. A liquid crystal display device using the flat light source according to claim 1 as a backlight.